Many sensors use so-called MEMS (Micro-electromechanical Systems) technology to achieve high performance electronic devices at a relatively low cost. One such sensor is a fluid pressure sensor that uses a MEMS pressure transducer, an example of which is disclosed in U.S. Pat. No. 8,466,523 entitled, Differential Pressure Sensor Device, the entire content of which is incorporated herein by reference.
Put simply, a MEMS pressure transducer comprises a small, thin silicon diaphragm onto which a piezoresistive circuit is formed, normally a Wheatstone bridge, well known to those of ordinary skill in the electronic arts. Diaphragm deflections caused by pressure applied to the diaphragm change the resistance values of the piezoresistors in the bridge circuit. An electronic circuit coupled to the bridge circuit detects the resistance changes of the piezoresistive bridge circuit and outputs an electrical signal, which changes with diaphragm deflections and is thus representative of the pressure applied to the diaphragm. The output signal is typically a D.C. voltage, the magnitude of which changes with applied pressure and thus corresponds to an applied pressure.
While MEMS pressure transducers have proven to be rugged, accurate, and relatively low cost, the signals output from a MEMS pressure transducer are usually non-linear. They can also vary widely and unpredictably between different MEMS pressure transducer devices. It is therefore often necessary to “process” a signal output from a MEMS pressure transducer in order to provide an electrical signal that varies linearly over a predetermined range of pressures applied to a MEMS pressure transducer.
Fluid pressure sensors that use MEMS pressure transducers typically perform various predetermined mathematical operations on the electrical signal output from a MEMS pressure transducer in order to provide a signal that varies linearly or at least substantially linearly across a predetermined range of pressures applied to a MEMS pressure transducer. Those mathematical operations are preferably performed by a digital signal processor (DSP), which is programmed with instructions, which, when executed, compensate or adjust the non-linear output signal from a MEMS pressure transducer to provide a signal that varies linearly across a range of pressures.
In some pressure-sensing applications, such as internal combustion engine fuel injection, it might be desirable or even necessary to provide a reasonably accurate measurement of fuel rail pressures that might vary between 1 bar (1 atmosphere) up to as much as 500 bar (500 atmospheres). For economy purposes or emission control purposes, however, it might be necessary to more accurately measure fuel rail pressures over different pressure ranges.
A problem with prior art pressure sensors that compensate the output of a MEMS pressure transducer using a processor is that the processors are unable to autonomously change their programming parameters according to different requirements in order to provide an output signal having greater accuracy over a narrow range of pressures. In other words, prior art pressure sensors that compensate the output of a MEMS pressure transducer using a pre-programmed processor are not able to provide a “dual range” or “multi-range” pressure sensing capability, i.e., a pressure sensor with different “sensitivities.” Stated yet another way, it would be an improvement over the prior art if a single pressure sensor housing, which could be attached to a pressurized fluid at a single location, could provide one or more different output signals, the output values which can range between the same lower and upper limits but responsive to different ranges of input pressures.